This invention relates to the preparation of cationic polymers having a surprising degree of effectiveness as sludge dewatering agents and certain other uses.
In particular, the cationic polyelectrolytes manufactured by the method of this invention are made from cationic monomers such as dialkyl diallyl ammonium monomers and, preferably, certain quantities of triallyl and tetraallyl ammonium monomers as branching agents. The advantages of emulsion polymerization of these monomers will become apparent in the summary of the invention.
Prior to the present invention, the water-in-oil emulsion polymerization techniques of Vanderhoff et al, U.S. Pat. No. 3,284,393, had not been extended to include such cationic monomers as the diallyl dialkyl ammonium halides. Vanderhoff disclosed in his U.S. Pat. No. 3,284,393 that a water-in-oil emulsion technique could be used to prepare polymers from certain water-soluble monomers. However, he did not teach the unique effect of such polymerization techniques on crosslinking of the monomers. Nor did he recognize that the diallyl monomers in particular are unusually receptive to the water-in-oil polymerization techniques.
Butler, in U.S. Pat. No. 3,288,770, disclosed a method of suspension polymerization of dimethyl diallyl ammonium chloride, using ethyl benzene as a solvent. There was no surfactant or emulsifier present in that example. The suspension polymerization method of Butler has never been used commercially because it provides no advantage over a simple solution polymerization method. Moreover, the suspension system of Friedrich et al as described in U.S. Pat. No. 2,982,749 has not been used commercially for the manufacture of cationic polymers for the same reason.